This invention relates to photographic exposure control systems and, more particularly, to an exposure control system having automatic control in both ambient and flash modes of operation.
The above-noted parent application describes a so-called "hybrid" exposure control system which is responsive solely to scene brightness in an ambient mode of operation and to both scene brightness and scene ranging in a transient, or that is, a flash illumination mode. In the above system, shutter-diaphragm blades are driven from a closed position toward enlarging aperture values and back to a closed position to define both a maximum aperture and an exposure interval. In a flash mode of operation, the maximum aperture is determined from scene ranging, or that is, in accordance with the anticipated level of flash illumination of the scene while the exposure interval is responsive to scene brightness whereas in the ambient mode, both the maximum aperture and the exposure interval are determined by scene brightness. Consequently, while the responsiveness to scene brightness is solely controlling in the ambient mode, it shares control with the subject distance selection under flash operation. Another example of a hybrid exposure control system is also described in U.S. Pat. No. 3,464,332 issued to Davidson et. al. on Sept. 2, 1969.
While the above systems provide a fully automatic camera operation, it is often desirable to provide a trim function to accomodate for slight variation in film characteristics as well as to insert operator control over the fully automated system. Further, it is desirable to provide a trim arrangement with only one manually adjustable control component. In more conventional exposure control systems which employ different control elements respectively in each of the two modes of operation, the provision of a trim control is known and is shown, for example, in U.S. Pat. No. 3,832,722 issued to Lawrence M. Douglas on Aug. 27, 1974.
For a hybrid system such as described in the parent application, however, the provision of efficient trim arrangement operable in both the ambient and flash modes of operation is complicated by the fact that the scene brightness sensing means is utilized in both modes of operation while scene ranging is operable solely in the artificial illumination mode.
Consequently, it is an important object of this invention to provide an improved hybrid photographic exposure control system suitable for both flash and ambient illumination.
It is another primary object of this invention to provide an automatic exposure control system having a trim arrangement suitable for operation in both ambient and flash modes.
A still further object of this invention is to provide a hybrid exposure control system having a unitary trim arrangement.